When packaging such fluid type of foodstuff into bags, the trouble which is usually encountered is that the foodstuff is liable to flow out of the bag if the bag happens to be slightly tilted. One attempt directed to preventing such a trouble is that, as described in U.S. Pat. No. 4,580,393, when vacuum packaging a foodstuff of such sort, a predetermined quantity of such foodstuff is fed into each bag while the bag is supported in suspension by clippers, and then the bag is delivered into a vacuum chamber as it is held in suspension by the clippers.
Such clippers are similar in construction to clothespegs, being such that a packaging bag is supplied into a narrow space defined between a pair of clippers in opened condition. With such clippers, however, the trouble is that since a flexible packaging bag has an inherent distortion, it is impracticable to expect that packaging bags can be fed with 100% accuracy to individual pairs of clippers during bag feed operation, it being thus likely that some clipping errors will take place. Once each bag is clipped in position by a pair of clippers, it is then required that opposite sides of the bag be sucked into a vacuum cup to thereby open the mounth of the bag through which foodstuff is to be placed as required. In this case, even if the bag is accurately clipped in position by the clippers, the vacuum cup operates to open the mouth of the bag immediately after it goes in momentary contact with the bag, for purposes of increasing the efficiency of packaging operation, with the result that the pressure in the interior of the bag becomes negative so that the bag is likely to get disengaged from the vacuum cup. Furthermore, since the foodstuff tends to set in spherical form at the bottom of the bag under its own weight as it is loaded into the bag, it is likely that the foodstuff will be vacuum packaged as it remains in spherical form in the bag.
In U.S. Pat. No. 3,488,914, a vacuum packaging apparatus is disclosed in which belt-like strips of film are delivered as they are gradually rounded into tubular form, and the tubulated pieces of film are cross-sealed to a predetermined length and successively formed into bags, the bags being filled with a fluid foodstuff which are in turn dropped successively into a vacuum chamber for vacuum packaging. This apparatus eliminates the necessity of each bag being grasped in position by clippers and the use of a vacuum cup for opening the mouth of the bag, and therefore it permits packaging operation with less error possibility. However, the apparatus has a disadvantage in that since belt-like strips of film are rounded to form bags, each bag has an overlapped film edge portion formed centrally therein, so that when the tubulated film is cross-sealed at opposite ends, the bag has portions different in thickness from its center overlapped portion, which often results in unsatisfactory sealing. As such, the apparatus has not proved successful for use in vacuum packaging operation.